For semiconductor devices such as LSIs, various types of ion implantation are performed on semiconductor substrates for the purpose of forming impurity diffusion regions such as wells.
Ion implantation apparatuses for use in the ion implantation are roughly classified into single-wafer type apparatuses and batch type apparatuses. Among these apparatuses, the batch type apparatuses are capable of performing the collective ion implantation on multiple semiconductor substrates, and are hence more efficient than the single-wafer type apparatuses.
The batch type ion implantation apparatuses have a mechanism in which multiple semiconductor substrates are disposed on the periphery of a circular disk, and are irradiated with ion beams while the disk is rapidly rotated.
A clamping mechanism is provided on the disk in order to fix the semiconductor substrates on the disk. The clamping mechanism prevents the semiconductor substrates from dropping off from the disk during the ion implantation.
However, if the clamping mechanism is not correctly aligned with an orientation flat of the semiconductor substrate, the semiconductor substrate cannot be fitted into a predetermined position of the clamping mechanism. As a result, the semiconductor substrate may possibly be dropped off. Additionally, with such incorrect alignment, the clamping mechanism can exert only an insufficient force to fix the semiconductor substrates on the disk. Consequently, the semiconductor substrate sometimes drops off from the disk, soon after a rotation of the disk is started.
In addition, since an ion implantation direction is determined depending on an orientation of the orientation flat of the semiconductor substrate, the orientation flat of the semiconductor substrate needs to be correctly aligned with the disk in order to form the semiconductor device having predetermined electrical characteristics.
It should be noted that the technologies related to the present application are disclosed in Japanese Laid-open Patent publication No. Hei 7-335585, Japanese Laid-open Patent publication No. 2004-253756, and Japanese Laid-open Patent publication No. 2005-203726.